The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Large, weighty batteries have been significant obstacles to realizing the full potential of various miniaturized electrical and mechanical devices developed in the recent, remarkable growth of micro/nanotechnology. Micro electro mechanical systems (MEMS) devices have been developed for use as various sensors and actuators; as biomedical devices; as wireless communication systems; and as micro chemical analysis systems. The ability to employ these systems as portable, stand-alone devices in both normal and extreme environments depends, however, upon the development of power sources compatible with the MEMS technology. In the worst case, the power source is rapidly depleted and the system requires frequent recharge for continuous, long-life operation.
A significant amount of research has been devoted to the development of higher energy density, light weight power sources. For example, solar cells can be used to provide electrical power for MEMS. Micro fuel cells have also been developed for many applications and a micro combustion engine has been reported. One of the major disadvantages of using chemical-reaction-based power sources is that the power density of the fuels gets lower as the size of the systems is reduced. A second major challenge is that the performance of these systems drops significantly when they are designed to achieve longer lives. In such cases, refueling (or recharging) is not a viable option because it cannot be done easily in tiny, portable devices. And finally, the aforementioned power sources cannot be used in extreme environments because either the reaction rate is influenced by temperature, and/or there is no sunlight available for powering the device.
Known radioisotope power sources were introduced in late 1950s. The concept of such direction conversion methods (alphavoltalics and betavoltaics) utilizes energy from radioactive decay. The radioisotope material emits α or β particles, which are coupled to a rectifying junction like a semiconductor p-n junction (or diode). The particles propagate to the rectifying junction and produce electron-hole pairs (EHPs). The EHPs are separated by the rectifying junction and converted into electrical energy.
Known crystalline solid-state semiconductors such as silicon carbides (SiC) or silicon based semiconductors have been formerly used for low energy beta voltaic cells using the rectifying junctions. However, one of the major drawbacks to using such known solid-state betavoltaic converters is that the ionizing radiation degrades the efficiency, performance, and lifetime of the conversion device. The primary degradation mechanism is the production of charge carrier traps from lattice displacement damage over the periods of time. Similarly but more seriously, high energy alpha particles can cause severe damage to the rectifying junctions of the solid-state semiconductors.